Method of packing catalyst

ABSTRACT

Provided are a catalyst packing method and a catalyst packing apparatus with which a desired packed density can be easily and surely obtained by use of a suspended type catalyst ejector, wherein correlated data giving a scattering height from which a desired packed density can be obtained has been determined and stored beforehand in a memory part 74, and by setting a desired packed density, prior to the scattering of catalyst, a selecting part 75 selects a scattering height corresponding to the desired packed density from the correlated data in the memory part 74 and delivers the same to an adjusting part 76 which controls the catalyst ejector 30 so as to obtain this scattering height, thereby the catalyst bed 11 in a reaction tower 10 can be packed at the desired packed density.

This application is a continuation of U.S. application Ser. No.08/297,115, filed Aug. 26, 1994, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of and an apparatus forpacking catalyst, which can be used in a work for packing particulatecatalyst in a reaction tower used in a petrochemical plant or the like,and so forth.

2. Description of the Related Art

A reaction tower in a petroleum refining plant, petrochemical plant orthe like is packed therein with suitable catalyst as necessary in orderto use the same for accelerating the reaction by a reaction solution.Particulate catalyst has been normally used in order to enhance theability of contact with the reaction solution, and has been packed inthe reaction tower at a predetermined density.

In a conventional catalyst packing work or the like, a worker in areaction tower suitably manipulates a hose through which catalyst is fedfrom an external hopper and which is led through an opening formed inthe upper part of the reaction tower, so as to scatter the catalyst, andthen he levels the surface of the catalyst in the tower.

However, with this conventional catalyst packing method, the followingdisadvantages have been offered. That is, since the worker carries outthe work with his labor in the reaction tower, the efficiency of workingis low, and since the worker treads the catalyst in the reaction tower,the packing density becomes nonuniform.

In order to eliminate the above-mentioned disadvantages, the applicantproposed a catalyst packing method in which a rotary scatter typecatalyst ejector is used (refer to Japanese Laid-Open Patent No.1-22807).

In this packing method, the rotary scatter type ejector for rotationallyscattering catalyst from a rotary ejection plate in the lower partthereof is suspended down from the top opening of a reaction tower, andthe suspended height of the catalyst ejector, the rotational speed ofthe ejection plate and the like are controlled so as to scatter thecatalyst in a multi-cylinder-like form in extent from the center to theouter periphery of the reaction tower, thereby it is possible to easilyensure a suitable and uniform scattering density and a uniform surfacelevel of the catalyst.

It is noted that the packing density of the catalyst is exhibited byweight/volume of packed catalyst, and as the packed condition, a maximumpacked condition in which the catalyst is laterally aligned in thereaction tower so as to give a maximum density, and a sock packedcondition in which the catalyst entangles with one another in thereaction tower so as to have a low density, are used.

These conditions as well as the value of density are suitably selectedin accordance with a kind of catalyst, a configuration of a catalysttower to be packed with the catalyst, a property of reaction solutionand the like.

By the way, in the above-mentioned rotary scatter packing method, theheight of the catalyst ejector from the surface of the catalyst bedduring scattering is controlled so as to be substantially constant, andso forth, in order to aim at uniformizing the density of packed catalysthaving been scattered.

However, the density of the packed catalyst, is determined in dependenceupon various terms such as a kind, particle size and specific weight ofcatalyst, a volume of scatter per hour of the same, a rotational speedof the catalyst ejector, a height of scattered catalyst and the like.Thus, these various condition have to be appropriately set in order toobtain a desired packed density although the uniformization of thedensity can be made by maintaining the various terms to be constant.

Such appropriate setting requires experiences possessed by a skilledperson, repetitions of trials each time when a packing work is carriedout, and the like, thereby it is difficult to surely and easily obtain adesired packed density of the catalyst bed.

A first object of the present invention is to provide a method of and anapparatus for packing catalyst with which a desired packed density ofcatalyst in a catalyst bed can be obtained by using a suspended typecatalyst ejector for scattering the catalyst in a reaction tower.

A second object of the present invention is to provide a method of andan apparatus for packing catalyst which can eliminate disadvantages suchas a complicated work for adjusting the length of a hose used forfeeding the catalyst into a suspended type catalyst ejector, inherent toa conventional packing work, the slack in the hose or the like duringpay-off or wind-up of the hose so as to facilitate the packing work.

A third object of the present invention is to provide a method ofinspecting the configuration of the outer surface of catalyst packed ina reaction tower, with which the configuration of the outer surface canbe surely inspected from the outside without the worker entering thereaction tower in order to visually check the configuration of thesurface of the catalyst or without the provision of camera or the likefor monitoring the inside of the reaction tower, and which can simplifythe apparatus and can enhance the working efficiency.

SUMMARY OF THE INVENTION

To the end, according to the present invention, there is provided amethod of packing catalyst in a reaction tower by scattering thecatalyst from a catalyst ejector suspended in the reaction tower,characterized by the steps of:

scattering catalyst from the catalyst ejector to form a catalyst bed inthe reaction tower;

controlling the catalyst density in the catalyst bed by controlling theheight at which the catalyst ejector is positioned above the catalystbed; and

moving a sensor substantially horizontally over the catalyst bed.

It is noted that the relationship to the scattering height, from which adesired packed density can be obtained, can be obtained beforehand byusing actual measurements under various conditions, accumulation ofempirical data given by skilled persons, those obtained by generalizingthese data and the like.

With these arrangements, since the relationship to the scatteringheight, from which a desired packed density is obtained, has previouslybeen determined, a desired scattering height corresponding to thedesired packed density is selected from the relationship in order tocontrol the catalyst ejector, thereby it is possible to attain thedesired packed density in the catalyst bed as the result of thescattering.

In this case, it is sufficient for controlling the catalyst ejector toselect the corresponding height in reference to the relationship whichhas been beforehand determined, so as to control it in order to alwaysobtain the selected scattering height. Accordingly, it is possible toeliminate the necessity of empirically setting by a skilled person, therepetitions of trails or the like each time when a packing work iscarried out.

Thus, it is possible to achieve the above-mentioned first object.

Further, according to the present invention, there is provided a methodof packing catalyst wherein the catalyst ejector connected thereto witha hose paid off from a hose wind-up mechanism provided outside of thereaction tower, is suspended downward from an opening in the upper partof the reaction tower so as to scatter the catalyst fed through the hoseinto the reaction tower by the catalyst ejector, a wind-up force whichis less than the weight of the catalyst ejector is effected in the hosewind-up mechanism always during scattering; the hose is wound up ontothe hose wind-up mechanism with the use of the wind-up force duringascent of the catalyst ejector; and the hose is paid off from the hosewind-up mechanism with the use of the weight of the catalyst ejector,overcoming the wind-up force during descent of the catalyst ejector.

With these arrangements, a predetermined wind-up force is always appliedto the hose extending to the catalyst ejector by the hose wind-upmechanism so as to automatically pay off or wind up the hose inassociation with ascent and descent of the catalyst ejector, thereby itis possible to prevent the hose from slacking in the intermediate partthereof and to eliminate the necessity of complicated control. Thus, itis possible to achieve the above-mentioned second object.

Further, according to the present invention, there is provided a methodof packing catalyst wherein a noncontact type distance sensor issuspended from the catalyst ejector in the reaction tower, the distancesensor being adapted to scan the outer surface of the catalyst bed inthe reaction tower after completion of scattering of the catalyst by thecatalyst ejector in order to check the configuration of the outersurface of the catalyst bed in view of distances to the outer surfacedelivered from the distance sensor.

Further, according to the present invention, it is characterized in thatthe distance from the distance sensor to the outer surface of thecatalyst directly therebelow is measured while the distance sensor isshifted in a substantially horizontal direction during scanning by saidsensor.

With these arrangements, the outer surface of the catalyst is scanned bythe distance sensor supported to the catalyst ejector suspended in thereaction tower so that the configuration of the outer surface can besurely checked from the outside of the reaction tower, thereby it ispossible to achieve the third object.

It is noted that the distance sensor is fixed in the vicinity of thefront end of a hold means for holding the catalyst ejector at the centerof the reaction tower, which radially extend and retract from thecatalyst ejector and which can make contact at its front end with theinner surface of the reaction tower, and the distance sensor is moved byextending and retracting the holding means so as to scan the outersurface of the catalyst in order to check the configuration thereof.

It is preferable to use, as a device for carrying out theabove-mentioned scanning, a device comprising a noncontact type distancesensor which is supported to the catalyst ejector suspended in thereaction tower, for scattering the catalyst, and which can scan theouter surface of the catalyst therebelow, and a process means forcontrolling the scanning of the distance sensor and for checking theconfiguration of the outer surface in view of distances to the outersurface which are delivered from the distance sensor.

Further, in this device, the distance sensor can measure a distance tothe outer surface of the catalyst directly therebelow, and is preferablysupported in the vicinity of the front end of the holding means whichcan radially extend and retract from the catalyst ejector and which canmake contact at its front end with the inner surface of the reactiontower.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating the entire arrangement of anembodiment of the present invention;

FIG. 2 is a block diagram illustrating a control means in the embodimentshown in FIG. 1;

FIG. 3 is a graph showing correlation data used in the embodiment shownin FIG. 1;

FIG. 4 is a front transverse sectional view illustrating a hose wind-upmechanism in the embodiment shown in FIG. 1;

FIG. 5 is a side transverse sectional view illustrating the hose wind-upmechanism in the embodiment shown in FIG. 1; and

FIG. 6 is a cross-sectional view illustrating the inspection for theconfiguration of the outer surface of catalyst in the embodiment shownin FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The present invention will be hereinbelow detailed in the form of anembodiment with reference to the drawings.

Referring to FIG. 1, a reaction tower 10 has a large bottomedcylindrical type, in which catalyst is packed, and is formed in its topsurface at the center of the latter with an opening 12 and is securedand supported at its bottom on a base 13.

A frame 14 is incorporated in the upper part of the reaction tower 10,and a catalyst packing apparatus 20 which is essential in the presentinvention is arranged in the frame 14.

The catalyst packing apparatus 20 comprises a catalyst ejector 30 whichis introduced being suspended in the reaction tower 10 for scatteringcatalyst in rotation, a chain wind-up mechanism 40 for winding up achain 41 which suspends the catalyst ejector 30 so as to move the latterup and down, a hopper mechanism 50 for supplying catalyst to bescattered, and a hose wind-up mechanism 60 for winding up a hose 61through which the catalyst is supplied to the catalyst ejector 30 fromthe hopper mechanism 50.

Further, the catalyst packing apparatus 20 incorporates a control means70 for controlling entire operation in accordance with outputs fromvarious sensors including a wire-like level meter 71 for detecting theheight of the outer surface of the catalyst packed in the reaction tower10.

The catalyst ejector 30 is adapted to scatter in rotation the catalystwhich is supplied through the hose 61, from an ejector plate 31 (FIG. 6)which is rotated in the lower part of the catalyst ejector 30. It ispreferable to use, as the catalyst ejector 30, a device which canscatter the catalyst in a multiple concentric circle-like pattern fromradially several positions, as is disclosed in Japanese PatentApplication No. 63-165577 belonging to the applicant.

Further, the catalyst ejector 30 incorporates three holding arms 35which radially extend for holding the center of the catalyst ejector 30at the center of the reaction tower 10. Each of the holding arms 35 hasa pantograph type expansion mechanism and has its front end part whichcan abut against the inner wall of the reaction tower 10 and whichcarries a roller so as to be vertically rollingable, and accordingly,the catalyst ejector 30 can be held at the center of the reaction tower10 by the extended holding arms 35 and is freely elevatable in thiscondition.

As shown in FIG. 6, a distance sensor 88 which is supported to the frontend 84 of each holding arm 35, is adapted to scan the outer surface ofthe catalyst bed 11 in the reaction tower 88 by extension and retractionof the holding arm 35, and accordingly, the control means 70 shown inFIG. 1 can measure the configuration of the outer surface.

Thus, in this embodiment, the configuration of the outer surface of thecatalyst packed in the reaction tower 10 can be surely checked from theoutside of the reaction tower 10 in such a condition that the catalystejector 30 is left to be in the reaction tower 10.

As shown in FIGS. 4 and 5, the hose wind-up mechanism 60 is adapted touse the hose 61 formed of a pair of belt members 62 which are joined atopposite sides by fasteners 63 so as to have a pipe-like shape, andcomprises a pair of reels 64 which wound thereon with the belt members62, respectively, a pair of air motors 65 which drive the reels 64,respectively, under the control of the control means 70, rollers 66 inpairs for guiding the belt members 62 paid out from the reels 64 so asto lead them along a pipe 51 extending from the hopper mechanism 50,joint members 67 for fastening and unfastening the fasteners at bothsides of the belt members 62 which are opposed together in a curvedcondition along the pipe 51.

Each of the belt members 62 is an anti-static type conveyer belt or thelike, and existing fasteners made of plastic or the like can be used asthe fasteners 63.

The joint members 67 correspond to worms on fasteners usually available,and fixed to the frame 14. Accordingly, the fasteners 63 are fastenedwhen they run downward through the joint members 67, but are unfastenedwhen they runs upward through the joint members 67 before they are woundon the reels 64.

Each of the air motors 65 is any of existing devices which generates aforce when compressed air is fed thereinto from the outside thereof. Ifcompressed air at a predetermined pressure is continuously fed to theair motor under the control of the control means 70, a desired rotatingdrive power can be maintained. Even in such a condition that this drivepower is held, the motor can be reversed if the load thereof increases.

Accordingly, upon descent of the catalyst ejector 30, the hose 61 isautomatically paid out by the weight of the catalyst ejector 30,overcoming the drive power of the air motors, and upon ascent of thecatalyst ejector 30, an extra length of the hose 61 is automaticallywound up by the drive power of the air motors 30.

The control means 70 controls the catalyst ejector 30 and the chainwind-up mechanism 40 in accordance with instructions and packing termsinputted from the outside, and the like, and accordingly, theintroduction and extraction of the catalyst ejector 30 into and from thereaction tower 10, and the work for packing the catalyst are carried outin a desired condition.

Accordingly, as shown in FIG. 2, the control means 70 comprises amanipulation part 72 including an input keyboard for inputting the termsfor packing the catalyst and the like, and a display for severalindications, an ejection control part 73 for controlling the volume ofthe catalyst ejected from the catalyst ejector 30, and the rotationalspeed upon ejection of the catalyst in accordance with a set term set onthe manipulation part 72, and a memory part 74, a selecting part 75 andan adjusting part 76 which control the chain wind-up mechanism 40 so asto adjust the suspension height of the catalyst ejector 30 in accordancewith a set condition on the manipulation part 72. The memory part 74stores therein correlated data exhibiting the relationship between thescattering height of the catalyst and the packing density, as shown FIG.3.

The correlated data are those which have been actually measured during atrial work which has been separately carried out beforehand. That is,the correlated data can be obtained by measuring variation in the packeddensity of the catalyst bed in such a condition that a kind, a particlesize and a specific weight of the catalyst, a scattering volume per unittime, and the rotational speed of the catalyst ejector are set topredetermined terms, respectively, and are stored in the form of anapproximated arithmetic function, a data table or the like from which ascattering height corresponding to an inputted arbitrary packed densitycan be obtained.

It is noted that from the correlated data shown in FIG. 3, such a factis found that the packed density of the catalyst bed becomes highest ina range above a scattering height of 1 m, and even at a height higherthan 1.5 m, the packed density becomes constant without exceeding 0.65.Meanwhile, in a range below a scanning height of 0.5 m, it exhibits asock packed density, and in each of ranges between these ranges, acondition intermediate between the highest packed density and sockpacked density is exhibited.

The selecting part 75 is adapted to select a scattering heightcorresponding to a packed density which has been designated inaccordance with a set term inputted through the manipulation part 72,from the memory part 74.

The adjusting part 76 adjusts the scattering height of the catalystscattered from the catalyst ejector 30 in accordance with the scatteringheight selected by the selecting part 75, that is, the height of theouter surface of the catalyst in the reaction tower 10 is measured bythe level meter 71, and a suspension height of the catalyst ejector 30is computed by adding the above-mentioned scattering height to theheight of the outer surface. Further, the chain wind-up mechanism 40 iscontrolled so as set the suspension height to the thus computed value.

It is noted that the adjusting part 76 repeats the above-mentionedcontrol for the scattering height when the height of the outer surfaceof the catalyst in the reaction tower 10 becomes a predetermined heightin advance of the scattering after the above-mentioned control.

In this embodiment, the catalyst scattering in the reaction tower iscarried out by the following procedure.

At first, the catalyst ejector 30 is suspended in the reaction tower 10by means of the chain wind-up mechanism 40 in such a condition that theholding arms 35 are retracted, and then the three holding arms 35 areextended in the vicinity of the bottom of the reaction tower 10 so as tohold the catalyst ejector 30 at the center of the reaction tower 10.

In this condition, the ejection control part 73 operates the catalystejector 30 at a predetermined rotational speed and ejection volume, andaccordingly, the catalyst supplied from the hopper mechanism 50 throughthe hose 61 is scattered in the reaction tower 10 with a multipleconcentric circle pattern.

In this phase, if a desired packed density is set on the manipulationpart 72, an appropriate scattering height is automatically set by theselecting part 75 and the memory part 74, and the suspension height ofthe catalyst ejector 30 is adjusted by the adjusting part 76 so as toset this scattering height.

That is, if a packed density of 0.6 is required, the scattering heightis set to 1 m in view of the correlated data shown in FIG. 3, Further,if a packed density of 0.65 is required, the scattering height is set toa value higher than 1.5 m. As a result, the packed density becomeshighest.

Meanwhile, a sock packed density is required, a scattering height lessthan 0.5 m is set in view of the correlated data shown in FIG. 3, and asa result, a height from 0.5 to 0 m is set in accordance with a densityof 0.55 to 0.5. In this case, the rotational speed and scattering volumeof the catalyst ejector 30 are increased in order to absorb a decreasein the rotationally scattering range due to a decrease in the scatteringheight.

The outer surface of the catalyst bed 11 in the reaction tower 10 risesup in advance of the scattering, and accordingly, the adjusting part 76detects the height of the outer surface of the catalyst 11 by means ofthe level meter 71, and raises the catalyst ejector 30 by means of thechain wind-up mechanism 40 each time when the increment of the height ofthe outer surface exceeds a predetermined value, thereby the scatteringheight is controlled so that it can be maintained at a set value.

With the repetitions of the scattering of the catalyst from apredetermined height and the adjustment to the height of the catalystejector 30, when the catalyst ejector 30 comes up to its ascent limit inthe reaction tower 10, the rotational speed of the catalyst scatteringis increased in accordance with a decrease in the scattering height dueto a rise-up of the outer surface of the catalyst bed 11 so as to ensurethe scattering range, and when the outer surface of the catalyst 11comes up to a predetermined height, the scattering is completed.

The above-mentioned embodiment offers the following technical effectsand advantages:

If a desired packed density is set, the control means 70 selects asuitable scattering height with which the, desired packed density can beobtained, and carries out the scattering operation in order to maintainthe scattering height.

Accordingly, the catalyst bed 11 can be packed in the reaction tower 10with a desired packed density having been set beforehand.

The packed condition of the catalyst bed 11 can be set to be a highestpacked density, a sock packed density, a packed density intermediatetherebetween or the like, thereby it is possible to surely and easilyobtain a desired packing result.

Meanwhile, upon the scattering, it is sufficient that the worker sets adesired packed density, a desired condition and the like through themanipulation part 72, and thereafter, the catalyst packing apparatus 20automatically carries out the scattering under the control of thecontrol means 70. Thus, the catalyst packing work can be easily andsurely carried out, thereby it is possible to enhance the workingefficiency.

In particular, since the control means 70 selects a scattering heightcorresponding to a set packed density from the correlated data shown inFIG. 3 which have been previously obtained by actual measurements, anappropriate scattering height can surely and rapidly set.

Accordingly, no skilled worker is required for the setting, but any onecan surely and rapidly set a suitable scattering height, and it ispossible to prevent erroneous discretion and manipulation or and thelike.

Further, the automatic process by the catalyst packing apparatus 20 canperform the scattering work which can give one and the same packeddensity, at a maximum speed, thereby it is possible to further enhancethe working efficiency in view of this point.

Further, since the distance sensor 88 supported to the front end of theholding arm 35 scans the outer surface of the catalyst bed 11 in thereaction tower 10 by the extension and retraction of the holding arm 35,the configuration of the outer surface of the catalyst bed 11 packed inthe reaction tower 10 can be surely checked from the outside, thereby itis possible to simplify the inspection device and to enhance the workingefficiency.

Further, in the hose wind-up mechanism 60, a predetermined wind-up forceis always applied to the hose 61 led to the catalyst ejector 30, by theair motor 65, and accordingly, the hose 61 is paid out, overcoming thewind-up force upon descent of the catalyst ejector 30 while an extralength thereof is automatically wound up by the wind-up force uponascent of the catalyst ejector 30, and accordingly, it is possible toprevent the intermediate part of the hose 61 from slacking and toeliminate the necessity of the manipulation for the adjustment to thelength as conventionally required, thereby the wind-up and the pay-offof the hose 61 led to the catalyst ejector 30 can be surely and easilycarried out.

It should be emphasized that the present invention should not be limitedonly to the above-mentioned embodiment, but may include the followingvariant forms.

That is, the correlated data for the scattering height which gives adesignated packed density, may not only be given by that shown in FIG. 3but may be suitably determined by each of other terms such a kind and aparticle size of catalyst, a rotational speed in scattering, and ascattering volume since the correlated data vary also depending uponthese other terms.

The correlated data may be prepared from previous actual measurementsunder various kind of terms, and in addition, may be obtained fromaccumulation of empirical data owned by a skilled person in accordancewith the other terms. Further, the correlated data can be obtained fromthe combination of both actual measurements and accumulation of theempirical data, and from the generalization of them.

Further, the correlated data may be stored in the control means 70 forevery other term so that the corresponding data are selected every timewhen the other term varies.

Further, it is sufficient, as to the type of the correlated data, tosuitably select those which complementarily uses a data tableincorporating discrete values, or those held as approximated values orthe like for every range, that is, it is sufficient to obtain ascattering height with which a desired packed density can be given.

Moreover, the correlated data may include not only the relationshipbetween the packed density and the scattering height, but also thosecorresponding to a part of the other terms.

For example, if a rotational speed necessary for scattering the catalystin a required area in the reaction tower 10 for every scattering height,is included, suitable setting can be easily and surely made in such casethat a process coping with a rise-up of the outer surface of thecatalyst bed 11 after the catalyst ejector 30 comes up to the upperlimit is carried out by changing the rotational speed.

It is noted that the arrangements of the components of the catalystpacking apparatus 20, such as the catalyst ejector 30, the chain wind-upmechanism 40, the hopper mechanism 50, the hose wind-up mechanism 60,the control means 70 and the distance sensor 88, the types of parts usedtherein or the like can use existing technique, and can be suitablyselected as actually required.

For example, an existing computer system or the like which has beensuitably set so as to perform the above-mentioned control can be used asthe control means 70.

Further, the catalyst ejector 30 should not be limited to the one havingthe holding arms 35, and further, the shape of the ejecting plate or thelike can be arbitrarily selected.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method of packingcatalyst in a reaction tower by scattering the catalyst from avertically movable catalyst ejector suspended in said reaction tower,comprising the steps of:supporting a noncontact type distance sensor onthe catalyst ejector for movement in a substantially horizontaldirection; scattering catalyst from the catalyst ejector to form acatalyst bed in the reaction tower; measuring the distance from thesensor to the surface of the catalyst bed; controlling the catalystdensity in the catalyst bed by controlling the height at which thecatalyst ejector is positioned above the catalyst bed; and at theconclusion of the scattering step, moving the sensor substantiallyhorizontally over the surface of the catalyst bed to scan and check theconfiguration of the surface of the catalyst bed.
 2. The method ofpacking catalyst as set forth in claim 1, wherein said catalyst ejectorconnected thereto with a hose paid off from a hose wind-up mechanismprovided outside of said reaction tower, is suspended downward from anopening in the upper part of said reaction tower so as to scatter thecatalyst fed through said hose into said reaction tower by said catalystejector, a wind-up force which is less than the weight of said catalystejector is effected in said hose wind-up mechanism always duringscattering; said hose is wound up onto said hose wind-up mechanism withthe use of said wind-up force during ascent of said catalyst ejector;and said hose is paid off from said hose wind-up mechanism with the useof the weight of said catalyst ejector, overcoming said wind-up forceduring descent of said catalyst ejector.
 3. A method of packing catalystas set forth in claim 1, wherein the distance from said distance sensorto the surface of the catalyst bed oriented directly therebelow ismeasured while said distance sensor is simultaneously moved in thesubstantially horizontal direction during measuring by said sensor.